The present invention is directed to a program-controlled communication system.
In communication network systems, such program-controlled communication systems which are also called program-controlled communication serve for the connection of terminal equipment to one another and for connecting these terminal equipment to communication networks, particularly public networks.
The multiplicity of known communication systems extends from simple telephone systems for the exclusive transmission of voice up to the fully expanded ISDN (integrated services digital network) communication systems having simultaneous multiple or mixed voice, text, picture and data communication. Terminal equipment having a great variety of performance features can be connected to the communication installation in an ISDN communication system, ranging from analog and digital telephones, telecopiers, multifunctional terminals, work station systems, personal computers, teletex and picture screen text stations up to data terminals. Such a communication installation is disclosed in a special edition of "Telcom Report", ISDN in the office, 1985, ISBN 3-8009-3849-9, Siemens AG.
The communication installation on which these communication systems are based is modularly constructed and essentially represents a digital computer system having a plurality of periphery units.
For the implementation of special services and jobs, modular units (servers) are provided within the framework of what is referred to as a server concept, these modular units assuming these special jobs with their own "intelligence". With an operations and data server, for example, performance features for an electronic data book, for functions for data acquisition, data processing and data transport as well as for the implementation of control jobs of connected computers are thus made available. A voice information server offers the connected subscribers the further possibility of rerouting their telephone connection to personal voice mailboxes. A text and fax server offers, among other features, performance features that implement a conversion of teletex to telefax when telefax-capable terminal equipment is not present at the receiver.
Each of these servers is fundamentally an autonomous computer system that is connected both in terms of software, as well as, hardware to a computer-controlled line switching unit of the communication installation. The terminal equipment are connected to the line switching unit that forms the basic module of the communication installation.
The program-oriented part of the communication installation, generally referred to as the software, is also divided into operations, administration and reliability modules in terms of job or, respectively, function orientation. A respective plurality of function-related program modules whose handling is coordinated in an operating system as tasks (processes) belongs to each of these modules in the line switching unit as well as in the servers. Since reactions within a prescribed time are frequently required in a communication installation, a real time operating system is used as an operating system, enabling a high reaction capability and providing a priority-controlled handling of program modules.
In order to assure, on the one hand, that incoming information is processed within a prescribed chronological duration, a correspondingly high priority level must be assigned to the program module provided for processing this incoming information. However, on the other hand program modules with lower priority levels should not be placed into a waiting condition for too long a time period by program modules having higher priority and should be handled at least within a greater time span.
For these reasons, in the prior art involved test phases have always been required for assigning the priority levels. In many instances, it only becomes clear during such test phases that the desired chronological behavior of the communication installation cannot be achieved with the program modules that have been provided, so that the program code of various program modules must still be altered after the fact, i.e. after the conclusion of the development phase of a communication installation.